This application relates to a method for detecting valve position in a valve driven by at least one electromagnetic coil, wherein changes in a signal applied to the coil are sensed.
For purposes of this application, the term xe2x80x9ccoilxe2x80x9d will refer to any type of device such as a solenoid, etc., which receives an electric signal to in turn move a plunger. The plunger may be a permanent magnet, or simply a material such as iron which is subject to magnetic attraction.
Valves are typically utilized in vehicle engines to control the supply of fuel and air to the engine cylinders. One type of valve is driven by a pair of coils, and is utilized as part of a fuel injector. In such a valve the two coils are selectively and alternatively powered to drive the plunger between two positions and control the supply of fuel. With such systems, it is very difficult to accurately track the timing of the valve, and to determine its position as it moves.
Other types of valves are driven by a single coil in one direction, and moved in the other direction by a spring force. The same concerns with regard to tracking the movement of the plunger exists in these systems.
Another application for vehicle control is the air supply and exhaust valves on an engine. Historically these valves have been controlled to open in sequence by a cam shaft and rocker arms. More recently camless control systems have been utilized. However, these camless systems have the same problem as mentioned above with regard to detection of the actual position of the valve plunger.
The present invention provides a simple method for detecting plunger position.
In a disclosed method and apparatus of this invention, two signals are supplied to a coil for driving a valve plunger. A first actuating signal powers the coil to drive the plunger. A second non-actuating signal is applied to at least one coil associated with the plunger. As the plunger moves, it will produce changes in this non-actuating signal. These changes are identified by a control such that by monitoring the changes the system will be able to predict at least when the plunger has approached an end of travel position. Most preferably, the change is compared to a reference signal.
In one embodiment there is only one coil for powering the plunger. In a second embodiment there are a pair of spaced coils. In this embodiment the non-actuating signal could be applied to the activated coil, or the deactivated coil.
In the embodiment having two drive coils, it could be the non-actuated coil which is utilized to provide the reference. In particular, a valve plunger other than the one that is being driven may also have a non-actuating signal applied to one of its coils. The changes in that signal are compared to the changes in the signal from the moving plunger coil. In this way, the system is better able to accurately track when changes in the non-actuating signal are in fact indicative of an end of travel position.
These and other features of the present invention can be best understood from the following specification and drawings, and the following which is a brief description.